image即时上传

function preview_upload(input, img_div_id){
        var img_id = img_div_id.replace("itempic_previewDiv", "itempic_preview")
        var width_str = "120px"
        var height_str = "120px"
        previewPic(input, img_div_id, img_id, width_str, height_str);
    }
    
    
    function previewPic(input, img_div_id, img_id, width_str, height_str) {
      //$("#localImag").html('<img id="img_prev" src="#" /><img src="/assets/touming.png"/>');          
      if (input.files && input.files[0]) {
        var reader = new FileReader();
        reader.onload = function (e) {
            $("#" + img_id).attr('src', e.target.result);
            };
        reader.readAsDataURL(input.files[0]);
      }else{
        // var imgObjPreview=document.getElementById("img_prev");
        var imgObjPreview=document.getElementById(img_id);
        //IE下，使用滤镜
        input.select();

        var imgSrc = document.selection.createRange().text;
        // var localImagId = document.getElementById("localImag");
        var localImagId = document.getElementById(img_div_id);
        //必须设置初始大小
        localImagId.style.width = width_str;
        localImagId.style.height = height_str;
        //图片异常的捕捉，防止用户修改后缀来伪造图片
        try{
          localImagId.style.filter="progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale)";
          localImagId.filters.item("DXImageTransform.Microsoft.AlphaImageLoader").src = imgSrc;
        }catch(e){
          alert("您上传的图片格式不正确，请重新选择!");
          return false;
        }
        imgObjPreview.style.display = 'none';
        document.selection.empty();
      }
      return true;
    }

html部分

<div class="by_jsq_top">
<div class="by_jsq_top_img" id="itempic_previewDiv"><img src="images/69.png" id="itempic_preview"></div>
<input type="file" name="user[logo]" class="file5" onchange="preview_upload(this, 'itempic_previewDiv')">
</div>

css部分

.file5{position: absolute; top: 80px; left: 50%; 40px; height: 40px; margin-left: -20px; opacity: 0;}